Submission #1093071

#	Time	Username	Problem	Language	Result	Execution time	Memory
1093071		TommasoUlian	Mobile (BOI12_mobile)	C++14	100 / 100	769 ms	51752 KiB

mobile

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
vector<pair<double, double>> torri;
ll n, L;

bool good(double r) {
    queue<pair<double, double>> q;
    double curr = 0;
    for (auto a : torri) {
        double x = a.first, y = a.second;
        if(curr >= L)return true;
        if (abs(y) <= r - 1e-6) { 
            double dx = sqrt((r + y) * (r - y));
            double a = x-dx, b = x+dx;
            q.push({a,b});
        }
    }
    while (!q.empty()) {
        if (curr >= L) return true; 
        auto seg = q.front();
        q.pop();
        if (seg.first-1e-6  <= curr) {
            curr = max(seg.second, curr);
        } 
    }

    
    return curr >= L; 
}

void solve() {
    cin >> n >> L;
    torri.resize(n);
    for (int i = 0; i < n; i++) {
        cin >> torri[i].first >> torri[i].second;
    }

    double l = 1, r = 2e9; 
    double ans = r;

    while (r - l > 1e-4) { 
        double c = (r + l) / 2;
        if (good(c)) {
            ans = c;
            r = c;
        } else {
            l = c;
        }
    }

    cout << setprecision(18) << (l + r) / 2 << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    solve();
    return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'void solve()':
mobile.cpp:41:12: warning: variable 'ans' set but not used [-Wunused-but-set-variable]
   41 |     double ans = r;
      |            ^~~

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